Automatic telephone-exchange apparatus.



F. R. McBERTY.

AUTOMATIC TELEPHONE EXCHANGE APPARATUS.

APPLICATION FILED APR. 20, 1909.

Patented Nov. 17, 1914.

4-SHBETS-SHEET 1.

Q Q 3 N ((kirceaaca P. R. MCBERTY. AUTOMATIC TELEPHONE EXCHANGE APPARATUS.

APPLICATKON FILED APR.20,1909.

4M z r m lw m 7 n w 4 Wm m M H 7 M m m R Q in fl .w

F. R. McBERTY.

AUTOMATIC TELEPHONE EXCHANGE APPARATUS,

APPLICATION FILED APR. 20. 1909.

LL I 46 f 9% :fl

Patented Nov. 17, 19l4 4 SHEETS-SHEET 3.

\ F. RFMOBERTY. AUTOMATIC TELEPEONE EXCHANGE APPARATUS.

APPLICATION IILED 'TAPR 20, 1909.

1,117,212. Patented Nov. 17, 1914.

4 SHEETS-SHEET 4.

UNITED sTATEs PATENT OFFICE.

vFRANK E. MCBERTY, OF NEW ROCHELLE, NEW YORK, ASSIGNOE TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

'AUTOMATIC TELEPHONE-EXCHANGE AQPPARATUS.

Specification of Letters i'atcnt.

Patented Now-1'7, 1914.

Application filed April 20, 1909. Serial No. 491,043. 7

"State of New York, have invented a certain new and useful Improvement in Automatic Telephone-Exchange Apparatus, of which the following 18 a full, clear, concise, and

- exact description.

call as in a manual system.

My invention relates to telephone exchange systems and contemplates an arrangement of circuits and apparatus whereby all the operations incident to testing, connection and restoration in a final selector are performed automatically, speedily and with absolute certainty.

- One feature of my invention is concerned with theprovision of improved and simple automatic means for testing a selected line, transmitting a busy signal to the calling station under the proper circumstances or completing connection to such selected line, applying ringing current there- -to, establishii'ig-telephonic transmission circuits uponfthe response of the called party, maintaining a'busy test upon the multi ple terminals of such line during connection, and finally restoring the apparatus and circuits to normal condition; these operatioxis being accomplished with precision, in definite order, and without the necessity of controlling action at the distant sending apparatus.

More particularly, my invention contemplates an arrangement of apparatus and cir cuits whereby a calling line may not only be connected with the particular'line selected, but if such selected line is busy and there are other lines which will as Well serve the purpose of the calling line,c"onnection will be established without any further controlling act with one of such lines, if one be idle, or, if all are found busyfa busy signal will be automatically operated.

The features of my invention ard inanifestly applicable both to systems of the .purely automatic type, wherein the select-Q ing switches are controlled by apparatus at the subscribers stations, and to systems of the semi-mechanical type, wherein the selecting switches are controlled by an operator at the exchange who has received the In ecor-dance with one feature of my present invention, the final selector, through which connection is to be made between a calling and a called line,-is adapted to ac commodate both ordinary subscribers lines and groups of trunk lines. By this means direct access is posibleby the calling line with either class of line. The selector is in itself provided with means whereby a dis criminatlve test is made in such a manner depend upon which class of line has been tested; the selector being provided with means whereby, if an ordinary subscribers line is selected by the external control, the connecting circuit from the calling-line will be connected to the line selected, if idle, and ringing current automatically placed upon the selected line; or if the line be busy, the selector will cause a busy signal to be sent back over the connecting circuit, but will not permit connection to be madebetween the connectingcircuit and the desired line,

the apparatus being thereafter restored to normal. \Vhen, however, theline selected that the further action of the selector will and tested is one of a group of trunk lines,

other than the lust of such group, if it is found busy the selector, instead of trans mitting a'busy signal, will proceed to test each of the trunk lines of that group until one is found which is idle, and will then connect therewith; or if none of such lines are idle, it will, after testing the last trunk line of the group,'then establish'a'busy signal, as in the case of a busy s'ubscriber's line.

My invention also involves means whereby, after a line is tested and found free, end the selector has completed a circuit to such line, it will establish a busy test condition upon all of the other terminals of such line to prevent the seizure of this lineby any other selector. '9

invention also involves means-whereby talking current is supplied to the called subscriber from a central battery, as is re-- quired by modern practice, the supply of "such talking current being underthe conlector by which the foregoing operations trate the preferred form of my invention,

show in addition various features which form no part of my present invention and are not claimed in this application. These features, however, are claimed in my appli-.

cations for Letters Patent as follows: Serial No. 418,123, filed February 27, 1908; Serial No. 418,124, filed February 27, 1908; Serial No. 418,120, filed February 27, 1908; Serial No. 451,867, filed September 5, 1908; Serial No. 451,868, filed September-5, 1908; and Serial No. 452,539, filed September 11 1908.

In the drawings Figure 1 is a' diagram illustrating an automatic selector or connector and its associated controlling apparatus and circuits; Fig. 2 is a diagram illustrating a' few of the line terminals upon the selector, together with the lines of different classes connected to the respective terminals; the connections being such as to enable the testing apparatus associated with the selector to discriminate between the different classes of lines and to govern the operation of such selector and its associated sig; naling apparatus accordingly; Fig. 3 is a view in elevation of one form of sequenceswitch which I prefer to employ for controlling the local operating circuits of the selector andits associated apparatus; Fig. 4 is a side view of the sequence-switch; Fig, 5 is a sectional plan view thereof on line 5-5 of Fig. 4; and Fig. 6 is a sectional plan View on line 6-6 of Fig. 4.

The same reference characters are used to designate the same parts wherever shown.

In the form of selector shown, the switch carriage or movable element of the selector is provided with a'number of multiple sets of brushes, any particular set of which may be selected for service, and the switch carrlage then advanced .over a series of sets of line terminals until the selected brushes are brought into engagement with the terminals of a desired line. In case the terminal so selected represents the first of a group of lines, such as trunks to a private branch exchange, any one of which Will serve the purpose of a calling subscriber, the s lector, in accordance with my invention, .1: enabled to make a further advance over the series of line terminals representing such group, under the control of local testing mechanism, until the selected set of brushes reaches a set of line terminals representing an idle line of the desired group.

To describe in detail the mechanism of the particular selector carriage, or brush carrying member, is of the rotary type, the frame being mounted upon a vertical rotary shaft 50. At the outer end of the frame a number of conn, the switch tact brushes 51, 52, 53, are mounted in position to sweep over sets of line terminals 61, 62, 03, which are fixed in an insulating frame concentric with the shaft. The contact brushes are pivotally mounted so that their free ends may be rocked outwardly into position to engage the ends of the line terminals which they pass over, or rocked inwardly so that they will not contact with such terminals. Spring tongues 54, 55, 56, respectively, press against projecting arms of the brushes, and besides making electrical connection therewith, tend to rock the brushes ontheir pivots .in a direction to throw their forward or contact ends outwardly. The brushes are electrically multiplied in sets of three, and each set is normally latched against the thrust of the spring tongues 55, 56, by a catch 57 which is normally held in .the path of movement of the rear ends of said brushes. As shown, the catches 57 are insulating bars mounted on spring latch-arms 58, which are the .free ends or tongues of a spring metal plate 59 fixed to the rotary frame 60. In order to bring any set of brushes into position to engage the contacts over which they travel, they must be released by tripping the corresponding catch 57 to allow the brushes to be'rocked upon their pivots by their springs 54, 55, 56. This tripping of the brushes is accomplished by a trip-bar 6 L which is pivotally mounted on an axis and has at its edge a series of projecting lugs 66 in position to be moved into the path of the respective latch-arms 58 when the trip-bar is rocked on its axis. a

It is intended that only one of the several sets of brushes shall be selected and tripped in a given operation, and the trip bar is therefore inclined at an angle so that the tripping lugs will face positions successively reached in the rotation of the brush carrier frame. The trip-bar will be actuated to thrust forward its tripping lugs only for a moment when the end of the latch-arm controlling the desired set of brushes reaches an angular position just in advance of that occupied by the particular lug which is at the proper height to engage that arm. The movement of the trip-bar may be accomplished by a tripping-magnet (57, the movable armature 68 whereof is mechanically connected to said bar.

A segmental metallic plate 70 's mounted in position to be engaged by the contact ends of the brushes as they plate extending to the end of the trip rangethat is, through the arc traversed by the brushes as one set after another through the series is brought into position to be tripped. At the end of the trip range the bank of line terminals 61, 62, 63, begins. These terminals are arranged in sets of three, correspondingin relative positions to sis in the action of a spring washer the i'ela.tive positions of the brushes by which the are to be trzniersed, and the dit ierent sets are arranged in an arc in position to l e u-cessircly reached in a point-toploint rotary advance of the brushes. To restore the brushes to their latched position when the selector returns to normal, an insulating bar 95 is arranged to he passed over by the lunslies in their return journex, the hrus-shes in passing (ner this bar being raised tl'ierehy against the tension of their springs, until their beveled rear ends slip over the catches 5?.

The motor merhanimn for rotating the brush carrier frame may he as follows: An iron plate 73 is mounted to rotate with the shaft 50, hut in such manner that it may be gri en a that wise or tilting movement into engagement with one or the other of two iron t'rictil'urdriving rollers Tel, 75, which are located on either side of its axis, said rollers being mounted upon a constantlyilriren poweusnatt TU. dill electromagnet 77, which 1 term the clutch magnet or power magn t. is arranged to nmgnetize the driving, rollers Tl and TI to cause them to attract the inn plate 73 Said plate is provided u it' l cam surfaces so that in the nor mal position of the apparatus the surface of the plate on one side 01' the axis 50 \Vlil he clos r to the dr; mg

surface on the other 7 3 of aid axis is to the driving wheel Tl. X u'nially, therefore. when the power magnet is excited the plate 75 will he drawn into engagement with roller 7.3 to reccire motion therefrom, and the carrier shaft 50 will he rotated in a clirection to admnce the hrunes After the brushes ha ve been advanced the distance required, the power r-luel T5 than the magnet will he deener nixed, the plate T3 uill he released from its engagement with driving roller T5, and said plate will recover from its tilted position 78. The cam surface of the plate being new augularly displaced from the (Us of the driw in; rollers, the body portion of the plate will be nearer to the rcturn roller Tl which is of larger diameter than the roller 75, so that when the po\\ er magnet is again energized the plate will he engaged by roller 74, and the shaft 30 will l r3 rotated thereby in a direction to return the rotary carrier to normal position.

A. cam St) carried hy the rotarv element of the selector to operate a snitch. On the first rotaiw movement. and while the brushes are passing the trip range. the cam lorces said spring Sl against an anvil H2. and at the end of the trip range the cam allows the spring" hi to recede from contact and ngage the alternate anvil S3. A malie and real; contact device or interrupler is also arranged to be operated as the brush-carrier 0f the selector rotates. As shown, an interrupter arm si is pl-utctl in the carrieri'rame simi arly t the ln'ushes 31, 52, 53,

un at its Ilia-Haul end a roller 8.3 al i h a laptcd to iuaiel over a t othed gamut therel r causing the arm to r1- illntt, As the roller rides up on each tooth. it rocks the a ontact RT. and this contact remains closed until the roller has passed over the tooth and has nearly reached the bottom of the following notch. spring tongue 91 which is mounted upon hut insulated from the frame '10. presses against and makes continuous elw'trieal connection with the c ntact arm W5. A pivoted arm 93, the tort of which rides upon the smooth rim of the toothed segment has a rearward extension which engages an ii'isulating stud carried by the arm as, to hold said arm against. the tension of the tongue 91. By this constr' i't'lOli the relative positions of the cont-ac an and H7 in any position of tho l rushcarxier frame depend solely upon the iclathe distance of the roller 83 fr m the rim of the toothed egment upon the edge of which it rides. and a re independent of slight variations in the radial distaucehetween said toothed segment and the axis of rotation of the Mush-carrier frame. The making and in! iii ll hrcals i of contacts 36 and 87 as the brush i irrier frame l'otat 4. is thus accurately lc lllulltl according to the cutting, of the net-Plies in the segment A spring tongue ft. mounted upon hut insulated from the lillSll-(MI'I led frame. and also insulated from tongue 91, hears upon the arm 93, and serves to make elect oral connection to the Contact point F 7, throl gh said arm 93, the rim of the metallic se 'inent 58 upon which it rides, the roller riding upon the edge of said segment, and arm 84 carrying said contact point, The terminal wires of the circuit to he interrupted by said contact 86, 87, are therefore soldered or otherwise connected to the tongues 91 and *2 respectively.

The brushes 51. 53, are electrically connected in multiple sets by the terminal plates ll, l2, 43, the plate 41 having tongues 54 making contact with all the brushes 5l,tl1e plate l2 haring tongues making contact with all the brushes 52, and plate 4.3 having tongues {)6 making contact with all the brushes 53. The two line wires and the test arni s-l in a direction to closesonable limits) as desired, and as many line terminals as desired in each level. The particular selector shown will have, for example, ten sets of brushes, and say ten sets of line terminals in each level; but for simplicity in the diagram there are illustrated only two of the ten sets of brushes and a few of the line terminals in each level.

The local controlling circuits at each selector which must be established in definite order at successive stages of the operation to bring into service different devices or parts, as desired, are, in the system in question, established by automatic switching appliances which I term sequence-switches, or electromechanical relays. There is a sequenceswitch for each selector, which consists in its elements of a movable switch operating member, a number of circuit-changers actuated in sequence as said member is moved from one position to another, an electromagnet, and motor mechanism operated or controlled by said magnet for advancing said movable member. In each position to which the movable member of the sequenceswitch is advanced, a set of circuits is es- I tablished by which a given operation of the device under control is made possible, and at the same time another circuit isestabllshed, whereby the motor magnet of the sequenceswitch may be actuated, so thattthe sequence switch will then be automatically advanced to the next position, in which a new set of circuits is established, bringing about a new operation or electrical condition of the device or devices under control, and so on. p

In the form of sequence-switch mechanism shown in Figs. 3 to 6 inclusive, the movable member is a 'vertical rotary shaft 7 carrying a number of switch operating cams 8, said shaft being arranged to be driven.

by power applied through the agency of an electromagnetic clutch. T he co nstantly driven power shaft 11 carries a frictlon driving disk 10 which is adapted to be drawn into engagement with a friction roller 9, carried upon the shaft 7, by the action of a clutch magnet 12. The roller 9 and the disk 10 are of iron, and the motor magnet 12 is adapted when excited to magnetize said roller, 9 which serves as a rotary pole piece for sai magnet; wherebythe driving disk 10 is attracted into engagement with said roller, the rotation of the shaft 7 thus continuing as long as the motor magnet 12 remains excited. The cams 8 carried by the rotary shaft 7 are arranged to operate; switc springs 13, forcing said springs into engagement with outer contacts 15, or allowing them to engage their alternate Inner contacts 14, according to the positions of said cams. As many cams and switches may be provided as the particular apparatus to be controlled may require. Certain of the switch contacts operated in the successive positions of the movable switch element may control circuits for the motor magnet 12. A special switch, such as shown in Fig. 6, is also preferably provided to control a local circuit for said motor magnet, whereby after the initial energizing circuit is broken by one or the other switches the motor magnet may still be excited. by current in the local circuit until the next intended stopping position of the rotary element is fully reached. As shown in Fig. 6, the cam 16 for operatin the local switch. is adapted to be engage by a cam roller 17 carried by a pivoted switch lever 18. A spring 19 is arranged to act upon said pivoted lever 18 so as to press the cam roller 17 against the edge of the cam 16. When the roller 17 rides upon a tooth or high part of the cam 16, said lever 18 closes a contact 20 which controls the local circuit for the motor magnet. inclined edges, so that the cam roller 17, after riding over the point of a tooth, is forced down the opposite slope by the action of the spring 19, and thus tends to push against the cam to continue the rotation thereof until the roller 17 reaches the bottom of the following notch. The rotary element is thus brought to rest accuratel in each of the positions where it is inten ed to stop. In the operation of the device, the circuit will first be closed for the motor magnet through one of the springs 13 and one or the other of the contact anvils 14 or 15 of such spring. Then, as the motor magnet is excited and the shaft of the sequence-switch begins to rotate, the contact through which the motor magnet was initially excited i'nay be broken, but the local circuit will be maintained for the motor magnet through the contact 20 closed by the cam 16, and the rotary element will thus continue to advance until the cam roller 17 reaches the bottom of the next notch of the cam Hi In the diagram Fig. 1 the switch springs of the sequence switch are not shown in their actual arrangement, but are so located as to a clear arrangement of the circuits and the operating cams are not shown. The positions of the rotary ele ment of each scquenceswitch in which any of its contacts (except contact 20) are closed, are indicated by numbers placed adjacent to such contacts; each contact being open in all positions except those indicated by reference numbers. F or example, contact 508 is closed in the first position, and in the 11th position, as indicated by the numbers 1, 11, placed adjacent thereto, and is open in all other positions. In the case of the special contact 20 operated by the "cam 16, the numbers are. placed on the op- The teeth of the cam 16 have which the contact is open, said contact being closed continuously while the rotary element of the sequence-switch is in transit be tween the positions indicated. It will he noted that the numbers are not consecutive between 5 and 13. but run 5. t 11. 13 and so forth. It will therefore he understood that the contact :20 is closed continu ously from the time the sequencc-switcll leaves the 5th position until it reaches the hilt. not stopping in the (5th. Tth or Sth positions. Said contact is also closed continuously from the time the Si."llltllUU-MYlU'li leaves the 9th position until it reaches the 11th, and also from the time it leaves the 11th position until it ieachesthe 13th. in the 5th, 9th. 11th and l lth positions. how ever, (and in all other positions the nurthers of which appear the contac' 2 open to permit the sen :tenceswitch to come to rest in the positions so indicated.

I have not illustrated in dctail'the send ing apparatus" for determin ng the select ing operation: but I have diagrammatically indicated certain switches for making changes in the electrical condition oi the main circuit at a distant point. such as would in fact he made by the controlling or sending apparatus. For the purposes oi this invention. it is immaterial how connection is made from the calling line to th trunk line 501.. 502. which terminates in the selector; and it is likewise immaterial what type of sending apparatus is used to control the selector. l hning selection such coir l'rol is effected from the different points hr the mere opening and closing of the circuit 501. 502. which terminates in the selec tor; and this circuit may he considered as a mere extension of the circuit from the calling line. After selection the control is effected by a ground connection associated with the conductor 501. This conne ,tion is shown diagranunatically at 1 52. It. will therefore be unnecessary to setforth the circuits. apparatus. and mode of operation of the complete telephone exchange: sullicient information being given herein to enable one skilled in the art to apply the present invention to an automatic exchangiv tent of any desired type. i

The apparatus and circuits to which I wish to direct particular attention are the two test relays Iii-l and Ilfll. with thbir connections and associated mechanism. and the connections of the test terminals of the lines shown in Fig. 2.

Referring first to Fig. it will he note-1i that of the live sets of line terminals shown.

the first set. (reading from left to right" represents an ordinary suhscrihcfs lline. The second. third and fourth sets of terminals represent three trunk lines respectively,

leading to a private branch exchange, and the fifth set of terminals represents another ordinary subscribers line. It will be noted that the test terminals (l3 of ordinary substaiheis lines are connected. through the cnt-oti i'tlzttw oi such lines. to the positive pole of a battery 300. the negative pole x hereof is groundcd. The same is true of the te t terminal f l" of the last of the group of three trunk lines hailing to the private branch exchange (l-.81 The test terminals Zil of :li the trunks except the last are con nccti-d. through the cutoi'l' relays of such il'lllilis at the central ollice. to the negative pole of a hatterv 301. the positive pole whereof is grounded.

Referring now to Fig. 1. it will be not d that two te t relays 323 and 391 are arranged to he c nnected in series in a test circuit which is compl ted from the test brushes 5 3 of the selector t earth, in certain po tions of the sequence switch. The relay 32-"? is a neutral relay. responding to current ofeither polarity: but it is of the marginal t vpe. heing adjusted to respond only when recehing the full current from the battery :luo or 301. through the cut-ofi' relay of a lin When the test brush of th selector is in contact with the test terminal of a line which already has a conncit 'in at some other set'of terminals. the test re ay ri-l w ill not receive the full current. since it is shunted hy the bath already established from another multiple terminal of the line tested. at the previously establislied connection. In testing a busy line, therefore. the marginal test relay will not respond. The relay 391 is polarized, and will respond only to current of the polarity which is derived from the test terminals (33" of all trunk lines except the last in each group: the last trunk line of each group having a potential applied to its test terminal of the same polarity as that which is applied to the test terminals 63 of ordinary lines. The polarized test relay ill)! will respond to current received from the test terminal of a line. whether such line is busy or not. The polarized relay il has. in addition to its main winding 39;. which is included with the relay 323 in the test circuit. a locking winding 393 01 feeble energizing power. This locking winding is sutlicieut ,to hold up the relay armature while the hrush is passing from one test terminal to the next. but is so ad jusied with respect to the winding 392 that upon the passage of current of the opposite polarity through the winding 392. the polarized test relay will he immediately deencrgized and the armature retracted. As will hereafter he descrihed in detail. the

two relays iii-l and 391 in the testing circuit act in combination to determine whether the selector shall seize the line :tested and transmit a ringing or calling signal to the called station, or whether a busy signal shall be sent back to the dis- ,180

tant calling or controlling point; or whether the selector shall further advance its brushes to the next set of line terminalsin their path, or an'intermediate trunk line, of a group leading to the same private branch exchange. 4

The operation of the selector and its associated a paratus is as follows: When the circuito the trunk line 501, 502,is completed at the distant calling or controlling point, a line relay 520 is excited by current from the free pole of grounded battery 50%, through the winding of said line relay, through one winding of a repeating coil 570, which inductively unites the two parts of the trunk line 501, 502, permitting the inductive transmission of telephone currents between the two sections thereof, to line conductor 501, and thence to the distant controlling point, where said conduc- .tor may be connected through a stepping relay 308 of a sending apparatus, and through the back contact of a stop relay 30$) 6f the sending apparatus, to the other line conductor 502, thence through another winding of the repeating coil 570, and through a normally closed contact 505 of the sequence-switch associated with the selector. to earth. The line relay 520, when thus excited, closes at its front contact a circuit from earth through a contact 508 of the sequence switch, closed in the 1st or normal position, through the motor magnet 507 of said sequence-switch, to the free pole of the grounded battery 506. The sequenceswitch is thereby moved to its 2nd position, in which contact 526 is closed, whereby the line relay 520, which remains excited, com pletes at its front contact a circuit from earth through said contact 526 and powermagnet 77 of the selector to the free pole of the grounded battery 525. The magnet 77 causes the power plate 73 of the selector to be drawn into engagement with the friction driving disk 75, which is constantly rotat ing, so that the rotary element or brushearrier of the selector is driven thereby, to advance the brushes. As soon as the brushcarrier begins to rotate, the cam 80 forces the contact spring 81 into engagement with the contact anvil 82, and thereby completes a circuit from ground through said contact 81, 82, through contact 532 of the sequenceswitch to the motor magnet 507 of said sequence-switch, and freepole of grounded battery 506. The sequence-switch is thus moved to the 3rd position, in which a set of brushes may be tripped. As the roller 85 of the interrupter rides over the toothed segment 88, the contact 86, 87, is alternately made and broken, and at each step a short circuit is thereby completed from line relay 520, through contact 522 of the sequenceswitch, back contact 528 of the trip magnet 67, and interrupter contact 86, 87, to earth,

short-circuiting the distant stepping mag net 308. Impulses are thus delivered to the stepping magnet 308 at the distant control ling point as the brush carrier of. the selector rotates, and these impulses may be used to control the selecting operation, by causing a step-by-step mechanism at the sender to operate in unison with the pointto-point advance of the selector.

When the sending apparatus has taken a predetermined number of steps, it may cause the stepping circuit 501, 502, to be broken, as b" J. relay 309. The breaking of this main qcuit will cause the line relay 520 at the elector to be released. This Wlll leave the trip magnet 67 connected in series with the power-magnet 77, over a circuit to ground through contacts 530, 551 and 553, said trip magnet having been short-circuited by the path through contact 526 of the sequence-switch and front contact of the line relay 520, until said line relay'was released. As the brush-carrier frame of the selector continues to rotate after the trip magnet 67 is excited by the removal of the short circuit controlled at the front contact of the line relay, the first of the latch arms to reach one of the tripping lugs 66 which have been thrust into the path of said latch arms by the trip magnet 67, will be engaged by such lug and detained sufiiciently to release the three brushes normally held by such latch arms. These brushes will thus be rocked upon their pivots by their springs 54, 55, 56, and their outer ends thrust into con tact with the grounded metal plate 70. The particular set of brushes which is thus brought into service will depend upon the number of steps through which the selector had advanced before the trip magnet was excited; that is to say, upon the number of steps which the sending apparatus took in unison with the selector before breaking the line circuit which released the line relay and caused the set of brushes to be tripped.

tram" When the test brush 53 of the set which is tripped makes contact with the grounded metallic segment 70 of the selector, a circuit is completed from battery 504, through the line relay 520, contact 538 of the sequenceswitch, plate 43 (which is connected through the tongues 50 to all the test brushes 53 in multiple) through the test brush 53 of the particular set which was tripped to the metal segment 70 and earth. This circuit causes the relay 520 to be again excited, re-

establishing the short circuit of the trip magnet at the front contact of said relay.

When the rotary element of the selector has advanced to such an extent that all the .brushes have been carried beyond the range of the tripping lug (although no more brushes can be tripped because the trip magnet has been released and its armature in recovering has retracted the trip bar 64) the iraiue. This test circuit cam flllOtYr the t n hi to :etarn int contact with anril l. This comple es e rcuit from ground through prin t and eontaet V e -nta i siouen esnitch to the motor magnet ui tlttlttii wherehr said F tl;lltl1 't---'\\iit'll l. moved to its lth p sition. in this position the trip magnet is hernianeutl rut out of tlli'itit h the opening: of eontaet .130.

In the type of selector lte-o1t in he ilrawinn. the se r-tent E i is r ruttul with an ext; notch in adrauee ot' the not .1 repre senting positions in whi h the elector lriislies rest up n the line itz'itltlizth. As

the brushes lea'w the fatll'lllElll il at the end of the trip range, the interiupter roller H rides up on a, long teot'h 9 ot' the rstglllt'lil 98. andhv ('lOsltttj centre-t 9h, ST. maintains a eireuit for the line l'-"ltt 520 through con tact 52:? ot the se uenee-auiteh. As the inlerrupte" roller 9 pa ses down from the long tooth into the t i notch in advance of the series, ot notehe eoire ponding to line t'ttlltCllllQ positions of the stl r hru lies. the cirerit controlled l the inti rt'upter t-ontact 9t 97. ls, hrolten. and the fir t ot a new series of selecting impulses is applied to the main cotuluetor 501 leading: arl; to the dis tant controlling peint. 'lhe eireuit will ha \'e heen attain completed at the sender or controlling point hi this time. so that the sending: apparatus will he again in condition to rec ive and resp' nd to selecting impulses. as before.

When he selector has advanced its brushes to the te minals of the desired line (this adranee having: heen mar-aired oil at the sending apparatus hy the impulses res eeived from the selector) the eireuit 50L 502, will he opened at the sending apparatus. as h the action ot' a stop rela 305 and a the interrupter roller 85 enters the notch in the toothed segment orrespondin to the position of the brush 'arrier in which the selected set oi hrushes rest upon the'terniinal ot the desired line, the contact 80. RT. is opened. and the'line relay .320 .i-: releas d.

iefore. however. the line relay 5:20 has heen teleased. a test circuit has heen completed at the contact 533:) ot the setpujnie switch. which circuit. under eontlitions to he des rihed. ill energize a relay hereinafter to close an alternative circuit to maintain the energizat ion of th power magnet 77 and continue the in rement of the hruslrearrier hurt he traced fr m the test terminal if the line upon the termi nals of which the hrushe rest. and to which a potential is supplied tjl'irougrh the cut-oil relay of such line t, the test brush Bil of the selector. Contact ot the :(ttlltilt0-?\\llCl]. windings of the test relav I t- "winding 392 of the polarized test relay. iwintact .353 of the sequence-switch, to earth. The alternative circuit referred to may l)t traeet] from bat- 2 power-magnet 77, front armature i-eutaet .nh ol' the p larized test relay 391, and hark ('Ot'itlt t 558 oi the test relay 323 to earth. 'lh t'ernatire circuit will onl he closed at such times as the polarized test rela Si l is energired and the test relay 322'- i. deFnergixed. Upon the release of the line relay 3:20. the circuit thr ugh the contact .3126 oi the sequence switch to the power magnet 77 is hrolten. and unless the alternative circuit to the power magnet has heen Closed, the ln'nsh-carrier frame will cease to rotate and the selected set of brushes will he hrought to rest upon the desired set of line terminals.

its the armature 01 the line relay 5530 reaches its hack contact a circuit is cont pleted from ground through the contact: 5:44. of the sequencoswiteh. to the motor magnet 30? and battery Sil whereby the sequence switch is moved to litth position. The test ircuit which r eoin iileted in the t'ointh position of the itltillt,--\ lit*ll l:-, maintained in the fifth position. .11" the liln .selected. and upon which the hrushys rest when the relay is released. an oxdinar suhserilwr s line and in hus neither test relay \1 ll .1- \e respondent and the alt-wine tin; circuit for energiyina inagne 77 will not he losed. since the e in through the test e -eit is ir ole the pro 'ie: polarity to energize the polari/etl rela bi l. If the line tested 18 an ordinary :z'iihi" l and is not busy. the test relay 1 alone will respond: in either of these cases the alternative Ciit jdit to the power magnet 77 not having been closed. the brush cart et frame will nio e no farther. If the line tested is the first li'lllllx line. or am intermediate trntil; line oi" a group. an ot which -\ill serve the purpose of the calling Filli'stl'llfi). as in ot a group of triitil-Ls leading to a private hraneh exchange. the polarired te t relay $91 will have responded. The man e'ii at test relay. however. will re pond onl in ase the line tested is tree. it the line tested is and therefore free the euergiicatiou of the test relay 33.; closure. of

will ha e prevented the the alternative circuit to the powenmagrnet, T7 and the lu-ash-earrier t'ranie will stop. If. however, the line terted is; hits the polarixed test relay having been energized has tlttrttl the alterna it'e circuit. to the power magnet T1 and the lti'tlhlt tftt t'ier frame will ontiniie to mo e until the liriishes rest upon the next set oi" terminals. at which time. and before the power-maanet T? has been allo.;-;-d to deenei ine. the test operation will be repeated. if the line tes ed is the linal trnnl line in a group of trunk lines. the Hint operation will he the same, as for an ordinary sulis rihefs line and need not be again. described.

As the sequence switch reaches its 5th po sition, in which the busy test is made. a circuit is completed for the motor magnet 507 of the sequence-switch, either through contact 541 and the back contacts 551 and 553 of the test relays 391 and 323, respectively, or through contact 540 of the sequenceswitch and front contact of the test relay 323, according as said test relay 323 is inert or excited. The scqiu-nce-switch is arranged to run through to its9th position, under control of the circuit through contact 541 and back contacts of the test relays unless suflicient current is received from the terminal of the tested line to energize the relay 323, or unless the line tested is a trunk line from the test terminal whereof a potential is derived of a, polarity suitable to operate the polarized relay 391.

In the 9th position of the sequence-switch, in which it stopped in case neither of the test relays is excited, a contact 5-12 is closed in which the free pole of the busy tone interrupter .360 is applied to the trunk line 5-02, to give a busy signal at the distant calling or controlling point in a well known manner. In case the line tested is a trunk line to thetest terminal 63 whereof a. negative potential is applied, which is the case with each trunk line except the last in each group. the polarized test relay 391 will be excited and will break the circuit for the motor magnet 507 before the sequenceswitch can leave the 5th position. If now the marginal test relay 323 does not respond, as in case the line tested is busy, the alterratiw circuit hereinbetore described will be completed from battery 52.3, through powerma .et 77 oi the selector, contact 558 of the polurirced test relay and back contact 3 of the marginal test relay, to earth. This circuit has been established before the power magnet 77 has released the power plate 73, and the brushes will not be allowed to stop upon the terminals of the trunk line so tested, but the rotation of the lu'ush-carrier will be continued until the test brush reaches the terminal of a trunk line of the group which tree. or until said test brush reaches the terminal ol' the last trunk line of the group. This last trunk line has its test terminal eonuected to battery ol the same polarity as an ordinary line. and if it is busy neither test relay 3:23 nor 301 will be excited. and the circuit for the motor magnet of the sequenceswitch will be completed through contacts 541, 551 and {353 in series, causing the sequencoswitch to run through to the 9th or busy back position. in which it will stop.

Immediately after the conclusion of each selecting operation which is determined by the opening of the circuit 501, 502, at the distant controlling point, a ground is placed upon the conductor 501, to cause the line relay 520 at the selector to be excited, this relay remaining excited during the.connection. This ground connection for. controlling the line relay 520 is located at the distant controlling point and need not be described, as it forms no part of this invention, but is shown diagrammatically at 452. When, as in the case of the failure to get a connection and the receipt of"-'a' busy signal at the controlling point, the connection with the trunk line 501, 502, at the controlling point is taken down, the ground connection 452 will be opened and the line relay 520 will be released and will cause the selector to be restored to normal condition, as will hereafter be described. In case the line tested is free, however, the test relay 323 in its response will close a circuit from ground through its front cbntact and contact 54:0 of the sequence-switch, to the motor magnet of said sequence-switch, and battery 506. 'lhe contact 540 remains closed from the 5th to 9th positions inclusive, of the sequence-switch, so that the latter does not stop in the 0th or busy back portion, but runs through to the 11th position, the local contact 20 being closed while the sequenceswitch is in transit between the 9th and 11th positions.

In the 11th position a circuit for the m0- tor magnet 507 mav be completed through contact 508 and the front contact of the line relay 520; and unless the connection has been prematurely taken down at the distant controlling point the line relay 520 Will still be excited, and the sequence-switch will continue to advance from the 11th position to the 13th, contact 20 being closed while the switch is in transit.

In the 135th position the contacts 536 and 537 are closed, connecting the poles of the ringing generator 556 to the line brushes 51 and 52 of the selector, thus applying ringing current to the called line. This ringing current will operate the call bell 571 at the substation of an ordinary subscribers line, or it will operate the annunciator drop 471 which is normally connected in the circuit of each trunk line at the private branch exchange. Upon the response of the called party in the usual nay, the closure of the circuit of the called line through the low resistance telephone apparatus at the called station causes an increased how of current through the supervisory relay 557, causing said relay to attract its armature. This completes a circuit from ground through the front contact of said supervisory relay, contact 543 of the sequence-switch to motor magnet 507 thereof and battery 506; Whereby the sequence-snitch is moved to the 14th position. In this position the contacts 561 and 562 are closed, completing the telephone transmission circuit for the trunk line from the repeating coil 570 through to the called line. Responsive to the operation of the two relays, that is, the supervisory relay 557 and the selector sequence-switch, as just described, talking current is supplied to the called party from battery 57].

When the connection is taken down at the distant calling or controlling point, and the ground connection of the trunk conductor 501 opened. the line rela .320 is released. and closes a circuit from ground through the back contact of said line relay. contact .384; of the S+ ll1t I]('.OS\\'ltCll to motor magnet no; thereof, and battery son. The sequenceswitch is therefore moved to the 15th position. in which contacts out and 162 are opened. and contact .376 closed, the latter completing a circuit from battery 5271, through the power-niagnet T7 of the selecto), contact Sit) and back contact of the line relay 52!) to earth. The power-magnet 77 s thus excited. and as the rotary element of th selector is now displaced from its normal position. the surface of the power plate l will he nearer to the retu'n roller Tl than it is to the driving roller 7.3, so that said plate 7 3 will be attracted into engagement with the return roller 74, and the brushcarrier is rotated back toward its normal position. 'hen the cam 80 in this return moacnient closes contact 81, 82, a circuit is completed from ground through contact E3 of the sequence-switch to the motor magnet 307 of said sequence-switch and battery 306, whereby the sequence-switch is moved to its 16th position. As the rotary element of the selector reaches its normal position the cam 80 allows the spring 81 to close against contact anvil t. thereby completing a circuit from ground through contact 533 of the serpience-switch to the motor magnet thereof, whereby the sequ nce-vitch is moved on to its normal position, having completed a full revolution. he whole apparatus has now been restored to normal condition. It will therefore appear that the terminals located in the selector may be divided into two classes or groups, first, those at which the movement of the brush-carrier must stop, such as those associated with ordinary subscribers lines and the last trunk line of a group of trunk lines. and those at which, if busy, it is desirable that the brush-carrier should continue in motion. It should be noted that in practice the cut-off relays connected to all of the first class or group of terminals are connected to one battery of the proper p0 larity, and all of those connected to the other class or group are connected to another batterv of the opposite polarity.

It will be observed that the supervisory relay 415 controls the supervisory lamp 413 and is in turn itself controlled by alterna tive circuits through the busy back and through the armature of the relay 557. 1he lamp 413 consequently serves at various times to indicate that the litre called is busy, that the party upon the line called has answered or that a disconnection is desired. This arrangement being simple and well understood will not be further described. it sill also he observed that the arrangemcnt whereby tl e line relay 520 and the test relay 323 control alternative controlling" ciruits at their from and ba lv' contacts, rc spectively. not only simplifies the circuits and reduces the amount of necessary appa ratus, but also renders the operation of such circuits and apparatus unerring and positive. This is particularly apparent in the case of the test relay. wherein the circuits which control the only two alternative operations necessary or possible at the time the test relay is brought into service. are closed by the armature of the relay at its front and back contacts. respectivehg depending upon .vhether or not the relay is energized. false or imperfect operation of the apparatus at this important stage in the opera ticn is. therefore. manifestly impossible. The same conditions e16 I in hardly less dc- ;Iree in connection with the line relay mo and the circuits controlled by it,

l'laving described my invention, what I claim as new and desire to secure by Letters latent is l. in a telephone exchange system, the combination with a selector having access both to ordinary subscribers lines and to groups of trunk lines. of contact brushes. means for advancing said brushes into contact with the terminals of the desired line. a circuit controlling the further advance of -iaid brushes, a test circuit. a test relay energized when the test circuit includes the test contact of one of a group of trunk lines other than the last of the g'rollp to close said circuit to furthe' advance said brushes, :1 locking winding on said relay in a local circuit and means for delinergizing said relay whcn the test circuit includes the test terminals of an ordinary subscriber's line or the last trunk line of a group.

2. In a telephone exchange system, the combination with an automatic selector, of lines terminatin therein comprising ordinary subscribers lines and groups of trunk lines, a test terminal for each line, a source of current connected with the test terminals of the ordinary subscribers lines and the last trunk line of each group of trunks, a source of current of opposite polarity connected with the test terminals of the trunk lines other than the last of the group, contact brushes in said selector, means for driving said brushes, :1 test circuit including the contact brush adapted to contact with the test terminals. and a polarized relay having two windings, one of said windings being included in the test circuit, the other of said windings being of feeble energizing power and included in a local locking circuit, said windings being such that the relay will be initially energized only when the test brush is in contact with a test terminal connected to the second mentioned source of current and such that when the test brush is in contact with a test terminal connected to the first source of current, the energization due to said locking winding will be over-balanced and the armature retracted.

In a telephone system the combination with a calling line, of a connectorv switch containing terminals of trunk lines and of ordinary subscribers lines, test terminals for said lines divided into two classes by reason of their being connected to sources of current of dillcrent polarity, a source of ringing current, a busy back, a sequence switch, a movable contact member for the connector switch, a test circuit, means including an electromagnetic clutch for advancing said contact member into engagement with a p edetermined line terminal so as to complete said test circuit, means for causin said sequence switch to move into busy bacl position when a busy line is encountered whose test terminal is of one class, means for preventing such a movement of the sequence switch it the test terminal encountered is of the other class, and for completing a circuit for the electromagnetic clutch whereby the movable contact of the connector switch may be advanced to test in succession a group of trunk lines until either an idle one is found or a test terminal of the first class again encountered, and means for thereupon advancing the sequence switch either to ringing or busy back position depending on whether or not an idle trunk has been found.

4. In a telephone system the combination with a calling line, of a connector switch containing terminals of trunk lines and of ordinary subscribers lines, test terminals for said lines divided into two classes by reason of their being connected to sources of cur rent of different polarity, a source of ringing current, a busy back, a sequence switch, a movable contact member for the connector switch, a test circuit, means including an electromagnetic clutch for advancing said contact member into engagement with a predetermined line terminal so as to complete said test circuit, means for causing said sequence switch to more into busy back position when a busy line is encountered whose test terminal is of one class, means for preventing such a movement of the sequence switch if the test terminal encountered is of the other class, and for completing a circuit for the electromagnetic clutch whereby the movable contact of the connector switch may be advanced to test in succession a group of trunk lines until either an idle one .5 found or a test terminal of the first class again encountered, and means for interrupting said. last named circuit upon the happening of either eventand permitting the sequence switch thereupon to advance either to ringing or busy back position depending on whether or not an idle trunk has been found.

5. in a telephone system the combination member for the connector switch, a source of ringing current, a busy back, a sequence switch having ringing and busy back ositions, at test circuit including a mar 'na test relay and a polarized test re ay, an circuits adapted to be completed in contacts of said test relays to determine, in accordance with the condition of the engaged test terminal, whether the sequence switch shall remain in testing position or go either to ringing or busy back position.

3. In a telephone system the combination with a calling line, of a power driven connector switch containing terminals of trunk lines and of ordinary subscribers lines, test terminals for said lines divided into two classes by reason of their being connected to sources of current of different polarity, a source of ringing current, a busy back, a sequence switch, a movable contact member for the connector switch, a test circuit including a marginal test relay and a polarized test relay, means including an electromagnetic clutch for advancing said contact member into engagement with a predetermined line terminal so as to complete said test circuit, circuits adapted to be completed in contacts of said test relays to determine, inaccordance with the condition of the engaged test terminal, whether the sequence switch shall remain in testing position or go either to ringing or busy back position, and, while maintaining said sequence switch in testing position, to also complete a circuit for the electromagnetic clutch whereby the movable contact member may be advanced until an idle trunk is found or all of them have been tested. I

7. In a telephone exchange system the combination with an automatic switch, of trunks and individual lines to be tested thereby, a sequence switch, a differentiating test means for determining, first, whether the trunk or line to which the switch has been directed is busy or idle, and if idle to cause said sequence switch to move to ringing position, second, if said trunk or line be busy to determine whether the contact is that of a trunk or' of an individual line, and if d a trunk to cause said automatic switch to test the trunk contacts one after another in search of an idle trunk, and when an idle trunk is found to then cause said so uence switch to move to ringing position, third, if

said line is a busy individual line or if no idle trunk line was found, to cause said sequence switch to move to busy back position.

8.;Ina telephone exchange system, the

a combination with a selector, of a motor mag- 10 ringing generator controlled jointly by said relays.

9. In a telephone exchange system, the combination with a selector, of a motor magnet therefor, a busy signal appliance, a ring- 'mg generator, test terminals and a test brush for saidsselector, sources of current of different character adapted to be connected to said test terminals, two test relays con-1' nected to said brush adapted to discriminate heiwur. the different sources of current, and local circuits for said motor magnet, busy signal appliances and ringing'generator controlled jointly by said relays.

In witness whereof, I hereunto subscribe my name this 19th day of April A. D., 1909.

FRANK R. MCBERTY.

Witnesses:

D. C. TANNER, F. T. WOODWARD. 

